Engineering Materials Lab Manual

8/17/2019 Engineering Materials Lab Manual

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COMSATS Institute of Information

Technology Sahiwal Campus

Lab Manual

Engineering Materials

COMSATS Institute of Information

Technology

COMSATS Road, O GT Road

Sahiwal


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Experiment No. 1

Objective

To determine the Hardness no of specimen by Rockwell Hardness test

Introduction

The Rockwell Hardness test is a hardness measurement based on the net increase in depth of

impression as a load is applied. Hardness numbers have no units and are commonly given in theR, L, M, E and scales. The higher the number in each of the scales means the harder the

material.

The i nden t o r i s s e l ec t ed depend i ng on t he na t u r e and cond i t i on o f

the material.!rale indentor, a conical shaped diamond penetrator with "#$ degrees ape% angle isused for steel and cast iron. & hardened steel ball '"(") inch diameter* is used for non+ferrous

metals. & minor load of "$ kg is first applied to take care of the roughness of the surface of the specimen

and the maor load is then applied ')$,"$$,"-$ kg*. The depth of indentation is recorded on

a dial gauge in terms of hardness numbers. Hardened steel is tested on scale with diamondindent or and "-$ kg maor load . /ofter materials are tested on the ! scale with ".) mm

diameter steel balland 0$ kg maorload.

Apparatus


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• Rockwell hardness tester and indentors

• specimen

Fig

Procedure

/elect suitable load and indentor depending on the nature of the material to be tested.

/ p e c i m e n i s p l a c e d o n t h e h a r d e n e d a n v i l o f t h e m a c h i n e w h i c h c a n b e

r a i se d o r lo w e r e d b y u s i n g a h a n d o p e r a t ed w h e e l s o t h a t t h e s u r fa c e o f th e s pec i me n u s t touches the indentor ,

/maller pointer in the dial starts moving and continues to raise theanvil slowly till the pointer comes to RE1 dot.This indicates that minor load '"$kg* hasbeen applied.

Turn the dial until the mark !+2$ '+$* and the word 3/ET4 is directly be hi nd th e

po i n t e r .

Re l eas e t he hand l e t o app l y ma o r l oad . Th e in de nt or st ar ts penetrating, which is read on the dial.

Remove the maor load by bringing back thehandle to the original position.

Read the position of the pointer on the scale, which givesRockwell Hardness 5umber.

Results


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Comments

!"ab Engineer#


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Experiment No. $

Objective

To determine the Hardness no of specimen by !rinell Hardness test

Introduction

Hardness is the measure of how resistant solid matter is to various kinds of permanent

shape change when a force is applied. Macroscopic hardness is generally characteri6ed by strong

intermolecular bonds, but the behavior of solid materials under force is comple%7 therefore, there

are different measurements of hardness8 scratch hardness, indentation hardness, and rebound

hardness. Hardness is dependent on ductility, elastic stiffness, plasticity, strain, strength,

toughness, viscoelasticity, and viscosity.

The !rinell hardness test is suitable for a range of materials

hardness9. !rinell hardness testing involves forcing a hardened

steel ball 'or a tungsten carbide ball for e%tremely hard materials*

into the surface of the specimen. The ball usually has a diameter

of "$mm and is pressed into the sample using a predetermined

load dependent on the relative hardness of the material e.g. -$$kg

for softer metals and 2$$$kg for hard metals.

The load is applied for a defined time, usually "$+"- seconds and

the impression diameter measured using a low power microscope.

http://en.wikipedia.org/wiki/Solidhttp://en.wikipedia.org/wiki/Matterhttp://en.wikipedia.org/wiki/Forcehttp://en.wikipedia.org/wiki/Intermolecular_bondhttp://en.wikipedia.org/wiki/Ductilityhttp://en.wikipedia.org/wiki/Elasticity_(physics)http://en.wikipedia.org/wiki/Elasticity_(physics)http://en.wikipedia.org/wiki/Stiffnesshttp://en.wikipedia.org/wiki/Stiffnesshttp://en.wikipedia.org/wiki/Plasticity_(physics)http://en.wikipedia.org/wiki/Deformation_(mechanics)http://en.wikipedia.org/wiki/Strength_of_materialshttp://en.wikipedia.org/wiki/Toughnesshttp://en.wikipedia.org/wiki/Viscoelasticityhttp://en.wikipedia.org/wiki/Viscosityhttp://en.wikipedia.org/wiki/Matterhttp://en.wikipedia.org/wiki/Forcehttp://en.wikipedia.org/wiki/Intermolecular_bondhttp://en.wikipedia.org/wiki/Ductilityhttp://en.wikipedia.org/wiki/Elasticity_(physics)http://en.wikipedia.org/wiki/Stiffnesshttp://en.wikipedia.org/wiki/Plasticity_(physics)http://en.wikipedia.org/wiki/Deformation_(mechanics)http://en.wikipedia.org/wiki/Strength_of_materialshttp://en.wikipedia.org/wiki/Toughnesshttp://en.wikipedia.org/wiki/Viscoelasticityhttp://en.wikipedia.org/wiki/Viscosityhttp://en.wikipedia.org/wiki/Solid


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H! : !rinell hardness

; : load in kg

1 : the diameter of the indenter in mm

1i : impression diameter in mm

Fig

Apparatus

• !rinell hardness testing Machine

• /pecimen

• alibrated optical microscope

P rocedure

• /elect suitable load and indentor depending on the nature of the material to be tested.

• /pecimen is placed on the hardened anvil of the machine, which can be raised

or lowered by using a hand+operated wheel.

• /pecimen is made to touch the indentor and the load is applied.

• &fter applying the load for thirty seconds, load is removed and the diameter of the

indentation is measured using microscope .!H5 is calculated using the above formula.


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Results

Comments

!"ab Engineer#


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Experiment No. %

Objective

To determine the Hardness no of specimen

by


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Apparatus

• uare base of "2) @ape% angle.

• /tandard test specimens

Fig

Procedure

• ;irst bring through A$9 of main scale to A$9 of vernier by operating the micrometer screw.

• !ring one edge of the s>uare base impression to coincide with main scale division by

operating the focusing screen screw.

• ount the number of M./.1. from the coincidededge to the division near the uncoincided

edge. This gives main scale reading.

• 5ow turnthe micrometer till the right edge coincides with ne%t forward main scale

division.

• 5owcount the vernier scale divisions from A$9 of main scale to A$9 of vernier scale.

•

Record the 5umber of divisions of the micrometer scale which is ust aheadand above A$9 inde% mark.

Results


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Comments

!"ab Engineer#


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Experiment No. +

Objective

To determine the Toughness no of specimen by =6od =mpact test.

Introduction

Toughness is the ability of a material to absorb energy and plastically deform without

fracturing. Material toughness is defined as the amount of energy per volume that a material can

absorb before rupturing. =t is also defined as the resistance to fracture of a material when

stressed.

The impact toughness of a material can be determined with a harpy or =6od test.

Two basic types of impact testing

1# Carp/ impact test0

• The specimen is supported as a simple beam with the load applied at the center.

• The position of latching tube is set to"B$@

• The specimen is supported hori6ontally from two sides

$# e I2od test0

• The specimen is supported as a cantilever beam.

• The position of latching tube is set to 0$@

• The specimen is supported


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• /pecimen.

Fig

Procedure

• /elect the test 'harpy(=6od*.

• /elect and fit the respective striker in the hammer, first tighten the screws of thewedge and

then of strikers.

• ;i% the latching tube to corresponding position 'for harpy "B$@ position and for =6od 0$@ position.• Clace a specimen on the support of the block.

• !ring the striker 'hammer* closely to specimen and tough it lightly with the specimen.

• Remove the specimen. Latch the hammer. Release the hammer. Hold back the releasing lever

• The pointer will show the frictional losses. This reading should be less than ".- oulesfor

harpy and $.D for =6od.


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Results

Comments

!"ab Engineer#


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Documents

Engineering Materials Lab Manual